1. Field of the Invention
The invention relates to a voltage converter, and more particularly to a voltage converter which provides various control schemes according to a load thereof.
2. Description of the Related Art
Nowadays, voltage converters are widely used in various electronic products, such as portable electronic products, computer products, and so on. Operating time of an electronic product is determined according to conversion efficiency of a voltage converter therein.
A pulse width modulation (PWM) controller is one type of control scheme for a continuous time voltage converter, which generates a PWM signal to control a transistor coupled to an output inductor of the voltage converter. By adjusting the duty cycle of the PWM signal, the PWM controller controls the transistor to turn on or off. Thus, the voltage converter may continually output voltage within a specific voltage range. For example, the PWM controller increases the duty cycle of the PWM signal when a load of the voltage converter is heavy. On the contrary, the PWM controller decreases the duty cycle of the PWM signal when the load of the voltage converter is light.
When the load of the voltage converter is light, the voltage converter may control the PWM signal at a minimal duty cycle. However, a continuous PWM signal requires power for the voltage converter, thereby decreasing the conversion efficiency of the voltage converter.
Therefore, a voltage converter which has improved conversion efficiency in a light load condition is desired.